1. Field of the Invention
The present invention relates to a serial printer for performing multicolor printing, and especially to a construction for a color ribbon cassette and also to an ink ribbon selection mechanism.
2. Description of the Related Art
Serial printers in the above field have conventionally included those making use of a ribbon cassette with a plurality of color ink feeding means provided therein. After the ribbon containing a desired color is positioned relative to a printing head, the ribbon is driven in unison with a printing operation so that printing is conducted while feeding an ink of the desired color to the ribbon. For example, Japanese Patent Publication No. SHO 63-35435 discloses one example of such ribbon cassettes. The construction and operation of the ribbon cassette disclosed in the above patent publication will next be described in brief. Plural transfer rollers are provided substantially in a central part of the ribbon cassette in such a way that the transfer rollers are stacked one over another and can rotate together. A plurality of color ink feeding means are arranged radially around the transfer rollers. A single, wide, endless ink ribbon is maintained in contact at transfer positions with roller surfaces of the transfer rollers by a biasing means. The transfer rollers also serve as a feeding means for the ink ribbon. When the transfer rollers are rotated in unison with a printing operation, the individual transfer rollers are impregnated with the respective color inks fed from the corresponding color ink feeding means, and the color inks are supplied to the ink ribbon at the transfer positions. An ink wick is provided between each color ink feeding means and its corresponding transfer roller. This ink wick can be separated by a change-over lever when it is not needed. The ribbon cassette can be shifted in a vertical direction relative to the printing head.
In such a conventional ribbon cassette, a single endless ribbon is employed by dividing it into different colors in parallel with the length thereof. If an operator forgets to separate, during printing, the ink wick for each color ink feeding means which is not needed for the printing, the color ink unnecessary for the printing is also supplied, resulting in the problem that the color ink so overfed undergoes "bleeding" to the adjacent color track or tracks.
The conventional ribbon cassette is accompanied by another problem that its dimensions become large as the color ink feeding means are arranged radially around the transfer rollers.